40 FRESH-WATER AQUARIA. 



objects. It should not be placed in a window having 

 a south front, as the light then is too strong, and will 

 develop that pest of aquaria, a thick opaque green- 

 Fig. 5- 



Oblong Tank for Window Aquarium. 



ness, do what we may. A northern aspect is always 

 the best for the glass frontages of aquaria to face, 

 whether they be placed in windows or in rooms. 



In the construction of square or polygonal aquaria 

 it is of course necessary above all things that the sides 

 should be perfectly water-tight. Leakage is a source 

 of annoyance and untidiness in a room, besides in- 

 terfering with that balance of animal and vegetable 

 life which is sought to be sustained in the water. The 

 following will be found a good receipt for making a 

 cement that will keep the sides and joints of a tank 

 perfectly water-tight : fine white sand, one part ; 

 litharge, one part ; resin, one-third part, mixed into a 



